DNA identification technology has numerous uses including identification of pathogenic organisms, genetic testing, and forensics. Advances have been made to allow for automated screening of thousands of sequences concurrently. Gene chip technologies exist where DNA probes are immobilized on a substrate such as a glass or silicon chip. A sample containing nucleic acid molecules is applied to the chip and the nucleic acid molecules within the sample are allowed to hybridize to the probe DNA on the chip. Fluorescence detection is typically used to identify double stranded nucleic acid molecule products. The advantage of the system is the ability to screen hundreds or thousands of sequences using automated systems.
Hybridization screening with fluorescence detection is a powerful technique for detecting nucleic acid sequences. However, in order to detect target DNA molecules, the target must first be amplified by PCR to get a reliable signal. The gene chip technology also requires a system capable of detecting fluorescent or radioactive materials. Such a system is expensive to use and is not amenable to a portable system for biological sample detection and identification. Furthermore, the hybridization reactions take up to two hours. For many potential uses, such as detecting biological warfare agents, the gene chip system is simply not effective. Therefore, there is a need for a system which can rapidly detect small quantities of a target nucleic acid molecule without relying on PCR amplification.
The present invention provides a method for detecting a target nucleic acid molecule. A device for detecting the presence of a target nucleic acid molecule is provided having two electronic leads, where the ends of the leads are located near each other but are not in contact. One or more sets of two oligonucleotide probes are attached to the electronic leads. The oligonucleotide probes are positioned such that the probes can not come into contact with one another and such that a target nucleic acid molecule, which has two sequences complimentary to the probes can bind to both probes concurrently. A sample which may have the target nucleic acid molecule is contacted with the probes under selective hybridization conditions. If the target is present it bridges the gap between the probes. The target nucleic acid molecule may then carry current between the probes, or be used as a support to form a conductive wire between the two probes.
The present invention also provides a device for detecting the presence of a target nucleic acid molecule. The device has two electronic leads, where the ends of the leads are located near each other but are not in contact. One or more sets of two oligonucleotide probes are attached to the electronic leads. The oligonucleotide probes are positioned such that the probes can not come into contact with one another and such that a target nucleic acid molecule, which has two sequences complimentary to the probes can bind to both probes concurrently.